1. Field of the Invention
The present invention relates to a photosensitive material drying device suitable for use in an automatic developing machine, for example, for drying a photosensitive material with radiant heat.
2. Description of the Related Art
In an automatic developing machine, photosensitive materials such as a photographic film (hereinafter called a "film"), photographic paper, etc. are subjected to developing, fixing and washing processes while being conveyed by rollers, and thereafter are transferred to a drying unit, where a process for drying the photosensitive materials is carried out.
Let's now take a film automatic developing machine as an example. In general, the drying unit is provided with a drying device, which has a plurality of far infrared radiation heaters disposed therein along the direction normal to a film conveying direction, i.e., along the transverse direction of the film, and a plurality of reflectors disposed on the far infrared radiation heater side opposite the film with the film interposed therebetween.
With this drying device, the radiant heat is directly radiated onto the film from the far infrared radiation heaters as far infrared radiation. In addition, the radiant heat is reflected by the reflectors so as to be indirectly radiated onto the exposed film. Afterwards, the film is heated and efficiently dried in a short time.
As represented by the graph in FIG. 8, a surface temperature t of a far infrared radiation heater is normally low at both ends thereof. Therefore, when the lengthwise dimension L of the far infrared radiation heater is set to a value substantially identical to the transverse dimension W of the film as in a conventional photosensitive material drying device (L.apprxeq.W) (see FIG. 9), a difference is developed between the amount of heat applied to transversely-extending ends of the film and the amount of heat applied to the central portion thereof.
When a far infrared radiation heater 72 is disposed in facing relationship to a film 74 along the transverse direction of the film 74 as shown in FIG. 9, far infrared radiations (see arrows 76) are radiated onto the film 74 from the far infrared radiation heater 72 in such a manner that the amount of the far infrared radiations at the central portion of the film 74 increases when compared to the transversely-extending ends thereof. Therefore, the amount of heat radiated onto the transversely-extending ends of the film 74 differs from that radiated onto the central portion thereof even if the surface temperature of the far infrared radiation heater 72 is kept constant along the longitudinal direction of the far infrared radiation heater 72. This creates a difference between the surface temperature at each of the transversely-extending ends of the film 74 and that at the central portion thereof.
Thus, when the surface temperatures of the film 74 are inconstant along the transverse direction of the film 74, an uneven dryness and glossiness is developed on the film 74. This causes a serious problem in view of the quality of the film 74.
Therefore, a photosensitive material drying device was proposed in a Japanese prior application filed by the present applicant, wherein the longitudinal dimension L of a far infrared radiation heater was made sufficiently longer than the transverse dimension W of a film and portions at which the surface temperature of the far infrared radiation heater is kept constant as represented by the graph in FIG. 10, were provided in facing relationship to the film along the transverse direction thereof. While this proposal undoubtedly improves the above problem it means an increase in the longitudinal dimension of the far infrared radiation heater. As a result, there is an increase in both the size and the manufacturing cost of the drying device. Thus, there is still room for improvement.